Flash an ESP32 from your browser
Synacl's ESP32 web flasher writes firmware to the board straight from
Chrome or Edge using the Web Serial API — no esptool, no drivers, no build tools. It runs in two
places: the public page at synacl.com/flash, which needs no account
and also flashes your own .bin files at any offset, and Gateways → Add gateway inside the app,
which flashes and registers a gateway in one go.
Flashing from the app
- Use a Chromium-based browser (Chrome/Edge). Web Serial isn't available in Firefox or Safari.
- Connect the ESP32 to your computer over USB.
- On Gateways → Add gateway, click Flash, then pick the serial port when prompted.
- The flasher writes the firmware and reads back the board's chip ID, which becomes the gateway's identity.
Flashing from the app needs the Provision gateways permission — the Owner and Admins have it; Operators don't. Team members whose role lacks it can still use the public flasher, which needs no account at all.
Next: provision Wi-Fi. If the port doesn't appear, see Web Serial isn't working.
Flashing without an account
On the public flasher pick Synacl gateway firmware and flash; the board
then sits waiting for Wi-Fi and account
credentials. When the flash finishes, the page offers Claim this gateway: it takes you through
sign-up (or sign-in) straight to Add gateway with the flash step already done and the Chip ID filled in from
the board's MAC, so you register it and provision it over the same USB cable. Chrome asks for the serial port again
there, because the app is a different site. To claim it later instead: open Gateways → Add gateway, skip step 1,
register the gateway (step 2) and provision it (step 3). The public page
also flashes your own .bin files at any offset, so it doubles as a general ESP32 web flasher.
For offsets by chip, USB drivers, the BOOT button and what each error means, see the guide
How to flash an ESP32 from your browser.
Re-flashing an existing gateway
You can re-flash a gateway that's already registered — useful when it can't take an over-the-air update because it's offline or stuck.
- Open the gateway's page and choose Flash via USB, or open Add gateway and pick it under "Re-flashing an existing gateway?". This needs the Provision gateways permission.
- A banner shows exactly which firmware version will be flashed before you click Flash.
- The build follows the gateway's firmware channel: a gateway on the Beta channel (with beta access enabled for your account) gets the latest beta build; otherwise the latest stable. New gateways always get stable.
- Re-flashing preserves the gateway's Wi-Fi and MQTT settings, so you don't need to re-register or re-provision it — steps 2–3 of the Add gateway page are only needed if you want to change those.